foo.cc: In function 'int main()':
foo.cc:13:24: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   13 |     while (numb.size() < k) {//TO DO:找序列前k个
      |            ~~~~~~~~~~~~^~~
foo.cc:22:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |     for (int i = 0; i < numb.size(); i++)//TO DO:int转string。
      |                     ~~^~~~~~~~~~~~~
foo.cc:35:14: warning: statement has no effect [-Wunused-value]
   35 |         for (i; i != n.end() ; i++)
      |              ^

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